534 ARCHEOLOGICAL INVESTIGATIONS—II [BTH. ANN. 44 
qualities of which have withstood the erosion that has worn away 
the underlying rock between them, until the topography of the 
region is as rugged as that in any other portion of the State. The 
map of the Missouri Geological Survey has this section marked as 
Cambrian, which may be true of all but the chert itself. This belongs 
to the St. Louis division of the Lower Carboniferous limestone. The 
space which it occupies is so restricted that it can not be represented 
on a map. 
The flint-capped area, with its windings and spurs, has a general 
direction toward the southeast. It has been compared to a skeleton, 
the main ridge representing the “ backbone” and the various spurs 
the “ribs.” The slopes are everywhere covered with an immense 
quantity of débris, part of which has rolled down from the outcrop 
at the top of the hill, but most of it resulting from the accumulated 
chert which remained when the limestone was dissolved and contin- 
ued as the surface rock when the general level was lowered. It is 
practically continuous and unbroken as far to the southward as 
High Ridge, 7 miles from the Meramec River. Throughout this 
length the hillsides are scarred with pits, the remains of aboriginal 
quarries. The upper layers, being porous from the weathering out 
of fossils, and also much checked and seamed by atmospheric action 
so that they easily shatter, are less suitable for making implements; 
consequently most of these depressions are toward the bottom of the 
deposit. Very few occur along the top of the ridge, and these only 
in places where erosion has removed most of the upper portion of 
the stone. The lowest stratum, about a foot in thickness, is a very 
compact, fine-grained stone, which has the texture, color, and chip- 
ping quality of chalcedony, and it was this which was most sought. 
Judging from the amount of waste in the form of spalls and blocks 
covering the hillsides below, a vast quantity of the chert was re- 
moved and thrown aside in order to reach that which possesses 
desirable flaking properties. After long exposure most of it has 
the appearance of chalk, though losing none of its hardness or 
fineness of grain. Asa rule it is quite white, but much of it weathers 
into various red or yellowish shades. 
Most of the quarrying was done on southern exposures, either be- 
cause the prevailing storms coming from this direction eroded more 
of the overlying material, thus bringing the flint closer to the sur- 
face, or because the work was done in the cool season in order to 
avoid the various bloodthirsty insects, both flying and crawling, 
which, in summer, swarm everywhere. 
The most remarkable feature about this deposit is its extreme 
thickness. In at least one place, despite the loss by denudation, it is 
fully 75 feet vertically from the crest of the ridge to the lowest level 
